@Femski001 I think you need to read the Terms & Conditions regarding data usage abroad. The description is far from inadequate, and does say that your data will be restricted. As far as I was aware unlimited only applies to usage while in the UK. If you're unhappy about your charges, there's a link to lodge a complaint within the link below:
There is no unlimited data tariff on PAYG.
If you use more than your UK allowances when abroad, you will be charged.
This is very clear in the T&C's.
You are also restricted to 20gb on PAYG when not in the UK but in Europe.
If outside of Europe, O2 travel rules apply which does give you unlimited daily data but which is almost impossible to use in excess as it is heavily throttled.